i think this is so important. I have known parents to 'force' kids to say hello or hug or kiss visitors in order that they not be rude, but to me it is just the first step in not allowing kids to set their own boundaries and respect the child's perception of people and right to to make guidelines for their own bodies.
I wholeheartedly agree, and have never allowed people to push the issue with DD if she doesn't want to go to them. Grandad used to be quite put out, till he realised if he backs off and lets her come to him she'll be all over him but if he tries to pick her up or grab her in a hug she gets intimidated and backs off. But to me, it's her right to decide who she wants to be friends with, and who she wants to give hugs or kisses to - I wouldn't expect an adult member of my family to give someone they don't know a hug just because I told them to, so why should I expect that of my child?

I do think with the keeping safe strategies like not going anywhere without letting mum/dad/supervising adult know it's FAR more than hints that's needed. It's open and frank discussion, teaching the rules directly that will make sure kids know where their boundaries are.